Supplemental Information (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	$ 34	$ 28	$ 31	$ 29
Bad debt expense	13	6	23	9
Charged to other accounts	1	1	1	2
Net write-offs	(9)	(5)	(16)	(10)
End of period	39	$ 30	39	$ 30
Payables for purchased receivables	$ 37		$ 37		$ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	26.00%	19.00%	26.00%	19.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 133	$ 107	$ 133	$ 107
Union Electric Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	12	11	13	13
Bad debt expense	2	2	4	3
Net write-offs	(2)	(1)	(5)	(4)
End of period	$ 12	$ 12	$ 12	$ 12
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	15.00%	14.00%	15.00%	14.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 28	$ 29	$ 28	$ 29
Ameren Illinois Company
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning of period	22	17	18	16
Bad debt expense	11	4	19	6
Charged to other accounts	1	1	1	2
Net write-offs	(7)	(4)	(11)	(6)
End of period	27	$ 18	27	$ 18
Payables for purchased receivables	$ 37		$ 37		$ 31
Percentage of accounts receivable balances that are 30 days past due or are part of a deferred payment arrangement	35.00%	24.00%	35.00%	24.00%
Accounts receivable balances that are 30 days or more past due or part of a deferred payment arrangement	$ 106	$ 78	$ 106	$ 78